Immunoglobulins (also called antibodies) are a group of structurally related proteins composed of heavy and light chains. These proteins are categorized as IgM, IgG, IgD, IgE, and IgA depending upon the characteristics of the constant regions of their heavy chains (designated μ, γ, δ, ε, and α, respectively). The variable regions of the heavy chains along with the variable regions of the light chains determine the molecular (antibody) specificity of the complete molecule. These molecules are secreted by B lymphocytes in response to signals from other components of the immune system. Their function is to prevent and combat infection by viruses and bacteria.
Purified IgG from pooled human plasma is administered intravenously in humans to treat a variety of conditions. In the purification, a fraction rich in IgA is considered an unwanted by-product, since intravenous administration of IgA-containing immunoglobulin G can cause life threatening anaphylaxis in some patients.
IgA on mucosa is produced locally and not derived from circulating IgA. IgA is one of the γ globulins on the basis of its electrophoretic mobility. IgA is composed of two α heavy chains and two light chains. It may be monomeric (i.e. a single molecule), dimeric (composed of two molecules) or trimeric (composed of three molecules). IgA monomers are joined together as dimers at the constant regions of their heavy chains by a J chain. IgA is secreted as one of two subclasses, IgA1 and IgA2. IgA1 predominates in the circulating blood wherein most of it occurs as a monomer. Most IgA on mucosal surfaces, such as the surfaces of the trachea, bronchi, and bronchioles in the lungs, occurs as dimers or trimers joined by J chains. IgA dimers and trimers have an increased ability to bind to and agglutinate target molecules (antigens). Agglutinated antigens are more readily phagocytosed and thereby eliminated. In addition, IgA dimers and trimers, because of the presence of their J chains, have the ability to attach to secretory component. Such molecules then have increased resistance to proteolytic enzymatic degradation. Human J chains (Symerski et al., Mol Immunol 2000; 37:133–140) and murine secretory component (Crottet et al., Biochem J 1999; 341:299–306) have been produced by genetic recombinant biological techniques. Recombinant expression of polymeric IgA with the incorporation of J chain and secretory component of human origin has been accomplished (Johansen et al., Eur J Immunol 1999; 29:1701–1708). Recombinant expression of antigen-specific monoclonal IgA bound to J chain within hybridoma cells before secretion has also been accomplished (Sun et al., Biotechnology 1995; 13:779–786 and U.S. Pat. No. 5,670,626 to Tse Wen Chang entitled “Allergen-Specific Human IgA Monoclonal Antibodies for Mucosal Administration”).
IgA can attach to the cell surface of phagocytic leukocytes and thereby facilitate antibody-dependent cell-mediated killing of microorganisms. It also interacts with lactoperoxidase and lactoferrin which enhances the latter's antibacterial actions. Monomeric IgA interferes with influenza virus replication (Taylor et al., J Exp Med 1985;161:198–209) and polymeric IgA interferes with influenza binding to and entry into target cells (Taylor et al., J Exp Med 1985;161:198–209; Outlaw and Dimmock, J Gen Virol 1990;71:69–76).
Tear secretory IgA enhances neutrophil chemotaxis (Lan JX et al., Aust N Z J Ophthalmol 1998;26 Suppl 1:S36–39). It inhibits Pseudomonas binding to the cornea and protects mice against bacterial keratitis (Masinick et al., Invest Ophthalmol Vis Sci 1997;38:910–918). Natural and monoclonal anti-Acanthoameba secretory IgA in tears inhibits Acanthoameba infection in hamsters by similarly decreasing binding of the protozan to the cornea. (Leher HF et al., Invest Ophthalmol Vis Sci 1998:39:2666–2773, Leher H et al., Exp Eye Res 1999; 69:75–84). Ocular secretory IgA also protects against ocular infection and establishment of latency by herpes simplex virus type 1 in mice (Richards C M et al., J Infect Dis 1998;177:1451–1457) and rabbits (Nesburn A B et al., Virol 1998; 252:200–209). Topically applied IgA (250 ug/ml) derived from milk inhibits binding of Pseudomonas to mouse cornea (Masinick et al., Invest Ophthalmol Vis Sci 1997;38:910–918).
Exogenous IgA has been topically applied to the nose in both animals and humans for the purpose of preventing and treating disease. In mice, nasal application of exogenous IgA has been demonstrated to be efficacious in protecting animals from influenza (Tamura et al., Vaccine 1990;8:479–485, Tamura et al., Eur J Immunol 1991;21:1337–1344), Sendai virus (Mazanec et al., J Virol 1987;61:2624–2626, Mazanec et al., Virus Res 1992;23:1–12) and respiratory syncytial virus (Weltzin et al., Antimicrob Agents Chemother 1994;38;2785–2791) challenge. Intranasal monoclonal IgA also protects rhesus monkeys against respiratory syncytial virus infection (Weltzin et al., J Infect Dis 1996;174:256–261). In humans, nasal administration of approximately 70% IgA/30% IgG resulted in decreased frequency of upper respiratory tract infections in elite skiers (Hemmingsson and Hammarstrom, Scand J Infect Dis 1993;25:73–75), and in children (Giraudi et al., Int J Pediatr Otorhinolarynol 1997;39:103–110, Heikkinen et al., Pediatr Infect Dis J 1998;17:367–372) but not in elite canoeists (Lindberg and Berglund, Int J Sports Med 1996;17:2335–238).
Aerosol administration of human γ globulin (Fruchtman et al., Clin Med 1972 (Sept);79:17–20), pooled human IgG (Rimensberger and Schaad, Pediatr Infect Dis J 1994;13:328–330) and murine recombinant humanized IgG (Fahy et al., Am J Respir Crit Care Med 1999;160:1023–1027) has demonstrated that there are no adverse effects from the aerosol inhalation of human γ globulin or human or humanized IgG. Topical administration of serum containing IgA to the surface of the eye has similarly demonstrated that there are no adverse effects from such applications (Fox et al., Arthritis Rheum 1984; 27:459–461, Tsubota K et al., Am J Ophthalmol 1996;122:38–52, Tsubota K et al., Ophthalmol 1999;106:1984–1989, Tsubota K et al., Br J Ophthalmol 1999;83:390–395).
Individuals suffering from hypogammaglobulinemia or with a local deficiency of IgA production such as that due to lack of tears, have been treated by a number of means, none of which has proven to be completely satisfactory. On the one hand, such patients have been treated by administration of antibiotics, either topical or local. However, antibiotic treatment is not completely effective in preventing infection in patients with immunoglobulin deficiency or whose immune systems are otherwise compromised. For example, infectious conjunctivitis is found in patients with lack of local immunoglobulin production.
Another method of treating such patients has been intravenous infusion of immunoglobulin. The immunoglobulin administered by intravenous infusion does not contain the secretory piece. As a result, the infused immunoglobulin may not reach the mucosal surface of a mucous membrane as found in the bronchial tree or eye. In addition, intravenous infusion of immunoglobulin is usually administered by trained medical personnel and can be associated with systemic reactions. There is thus a need for methods which can be used to deliver IgA to mucosal surfaces such as the bronchial mucosal and ocular conjunctival surfaces. It would be advantageous if such treatment could be administered by the patient without the need for intervention by trained medical personnel. It would further be desirable to make use of unwanted by-products resulting from the preparation of purified immunoglobulin G from pooled human plasma. The present invention provides these advantages and others as will be apparent to one with skill in the art from the disclosure that follows.